This invention will be particularly discussed in relation to stent grafts for placement into the thoracic abdominal aorta or into the abdominal aorta for the treatment of aneurysms. The invention, however, is not so restricted and may be applied to stent grafts for placement in any lumen of the human or animal body.
The positioning of stent grafts is very important for a number of reasons including in many cases the need to avoid occlusion of branch arteries. Positioning is complicated however because the diameter of a stent graft is deliberately made larger than the diameter into which it is to be placed to allow for accurate sealing against the vessel wall, possible errors in sizing and subsequent relaxation of the vessel wall.
Once released from a delivery device, a stent graft with self-expanding stents will take up apposition against the vessel wall and it will be difficult if not impossible to reposition it. This can be dangerous if, for instance, renal arteries are occluded.
Stent graft assemblies with diameter reducing ties have been developed to assist surgeons with the task of positioning stent grafts after initial release from a deployment device. Sewing and positioning of such ties during manufacture can be difficult and time consuming. Furthermore, errors in this process can have adverse effects.
It is an object of the invention to address difficulties described above while at the same time improving safety and simplifying assembly or to at least provide a useful alternative assembly technique.
Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis is the end of the aorta, deployment device or prosthesis further away in the direction of blood flow away from the heart and the term proximal means the portion of the aorta, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels similar terms such as caudal and cranial should be understood.